It is a screwdriver specifically for your needle. The needle screw has a small hole in it so the screwdriver sets in solid for you to tighten the screw. I loved that little thing when I had my Bernina. I gave it to a friend that sews and her machine had died and could not be fixed. She is a single Mother with children and sews for all of them and her home. She needed it and I had other machines. So it went to a very good home.